A.C. dielectric and TSC studies of constrained amorphous motions in flexible polymers including poly(oxymethylene) and miscible blends
✍ Scribed by Bryan B. Sauer; Peter Avakian; Edmund A. Flexman; Mimi Keating; Benjamin S. Hsiao; Ravi K. Verma
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 319 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0887-6266
No coin nor oath required. For personal study only.
✦ Synopsis
Poly(OxyMethylene) (POM) and its miscible blends were studied by multifrequency A.C. dielectric and thermally stimulated currents (TSC). The blends contained small amounts of either poly(vinyl phenol), which is a high glass transition (T g ) diluent, or a styrene-co-hydroxy styrene oligomeric low T g diluent. The variation of the 10ЊC ''b'' transition with blend composition proves that it is the glass transition, and that the 070ЊC ''g'' transition is a local motion. Dielectrically the b transition is very weak in pure POM even in fast-quenched samples. The TSC thermal sampling method also detected two cooperative transitions, g and b, in POM and its blends, and was used to directly resolve the g transition into low and high activation energy components. If one considers the contribution of exclusion of the diluents from the crystal lamellae, it is shown that the blends behave like typical amorphous blends as a function of concentration. The effect of crystals on amorphous motions is examined in light of comparison with van Krevelen's 37 predictions of an ''amorphous'' T g , and the transitions in POM are contrasted with those for other semicrystalline polymers.